Coupling of Free-boundary-equilibrium and Transport Solvers to Enable Model-based Scenario Optimization and Integrated Control

X. Song, B. Leard, Z. Wang, T. Rafiq, E. Schuster

29th IAEA Fusion Energy Conference

London, UK, October 16-21, 2023

Abstract

A coupling architecture has been developed to integrate the free-boundary equilibrium (FBE) and transport solvers in COTSIM (Control-Oriented Transport SIMulator). The coupling strategy employs different techniques to make the 2D equilibrium and 1D transport partial differential equations (PDEs) work in a self-consistent way. Sophisticated approaches are employed not only to accelerate the iterations for the FBE solver but also to compensate for deviations in the poloidal flux function at the plasma boundary between the equilibrium and transport solvers. Scaling laws and surrogate models for non-linear current density and heating sources make it possible to calculate transport equations in a fast way. As an illustration of a potential application, a dedicated simulation based on the integrated scheme is performed to study the EAST scenario from ramp-up to flat-top phases. The simulation results demonstrate that self-consistent parameters and profiles are achieved between the equilibrium and transport solvers. The integration of various dimensional solvers within COTSIM makes this platform uniquely qualified for two purposes: firstly, for model-based optimization of advanced scenarios, characterized by specific plasma shapes and core profiles achievable within actuator limits; and secondly, for model-based design and testing of integrated equilibrium and scenario feedback control solutions.